AFE converters are power electronic components used in power electronic systems. Such an AFE utilises power semiconductor devices controlled by signal electronics, followed by a filter circuit. Moreover, an AFE allows bidirectional power exchange between AC voltage source and DC-link. AFEs can also be coupled in parallel, but in order to do so, a paralleling control method is needed.
Previously a paralleling control method for paralleled AFEs connected to the same AC voltage source and same DC-link has been applied. This method adjusts the pulse width modulation (PWM) period length to minimize circulating common mode current, which effectively synchronises the triangular PWM carriers. According to this method, paralleling of AFEs without the need of interconnecting the control systems is provided. By omitting the interconnection of control systems enables a better scalability, but makes load balancing more challenging.
Usage of modern low inductance magnetics, such as powder cores, in combination with faster switching power electronics will result in a lower common mode inductance. Any error in DC voltage feedback will thus result in the common mode current being much greater compared to a design solution with low switching frequency and high filter inductance. A higher common mode current will result in higher losses in the converter, thus the efficiency of the AFE will be reduced. Therefore, a new method is needed in order to reduce these common mode currents in order to improve the efficiency of the AFE.